1. Field of the Invention
The present invention relates generally to so-called horizontal bandsaw machines and, more particularly, to bandsaw wheels or pulleys of such horizontal bandsaw machines around which endless bandsaw blades are trained.
2. Description of the Prior Art
The type of horizontal bandsaw machines with which the present invention is concerned are provided with a saw head assembly including bandsaw wheels or pulleys which are mounted for rotation on spaced substantially parallel axes and around which an endless bandsaw blade is trained. One of the bandsaw wheels is driven and acts as a driving wheel to drive the bandsaw blade through frictional engagement between one flat side of the bandsaw blade and the peripheral face of the driving bandsaw wheel. Also, in order to adequately tension the bandsaw blade, one of the bandsaw wheels is drawn or biased together with its shaft in a radial direction away from the other wheel. Furthermore, one of the stretches of the bandsaw blade between the bandsaw wheels is slidably guided and held by a plurality of guide means with its flat sides perpendicular to a work table on which workpieces to be cut are placed. Thus, the horizontal bandsaw machines are so designed that the saw head assembly is lowered towards the work table so that the bandsaw blade travelling around the bandsaw wheels may cut the workpieces placed on the work table.
Such horizontal bandsaw machines have been much improved after continuous efforts over a long period of years and they are now widely used in many industries and at many large and small factories and shops as the most advantageous and economical means for cutting a wide variety of materials.
Unfortunately, however, certain problems with these known horizontal bandsaw machines have remained unsolved, particularly with regard to the bandsaw wheels which are the most fundamental elements thereof.
One of these problems lies in the fact that the bandsaw blade will produce a very keen screeching noise especially on the bandsaw wheels when making cutting operations. This noise is caused primarily by the fact that the bandsaw blade vibrates severely against the peripheral surfaces of the bandsaw wheels during the cutting operations. This noise is apt to become an issue as a noise pollutant, especially since the bandsaw machines are very widely used even at small factories and shops in non-industrial areas.
The vibration of the bandsaw blade causing the keen and screechy noise occurs primarily from the fact that the bandsaw blade will be vibrated inherently because of its flexible nature not only sidewise or laterally but also breadthwise or vertically when making cutting operations. Blade vibration is increased or amplified because of the fact that there is a larger tensile stress in the stretch of the bandsaw blade leaving the workpiece as compared to the stretch approaching the workpiece because the bandsaw blade is driven and pulled by the driving bandsaw wheel under a strong tension. Accordingly, the vibration and the resultant noise of the bandsaw blade occur most severely where the bandsaw blade is cutting into the workpieces. Although the undesirable vibration of the bandsaw blade is reduced by the sawblade guide means for slidably guiding the bandsaw blade, the fact is that the vibration is too severe to be desirably reduced only by the guide means.
In addition to causing the above-described noise, the vibration of the bandsaw blade also has a bad influence on the rate and accuracy of the cut, as well as on the life of the blade. Also, blade vibration causes spraying of the cutting lubricant. Vibration of the bandsaw blade will also produce a rough cut, with the entry end of the kerf being wider than the remainder, making it difficult if not impossible to obtain a smooth straight cut. Since as mentioned above, the bandsaw blade is vibrated in two planes (sidewise and breadthwise) and thus is apt to be floating, the cutting rate also will be adversely affected. Also, the sidewise vibration of the bandsaw blade will result in excessive blade wear. Furthermore since the vibrating bandsaw blade will spray the cutting lubricant like a mist, the lubricant is lost out of the bandsaw machine without being recovered and splashes the operators and the surrounding environment of the bandsaw machine.
Another bothersome problem of the conventional horizontal bandsaw machines is the fact that the bandsaw blade is apt to slip on the bandsaw wheels. Such slippage results from the fact that the bandsaw blade is always flooded or bathed with cutting lubricant during cutting operations and such lubricant is carried onto the peripheral surfaces of the bandsaw wheels by the bandsaw blade and consequently a film of the lubricant will be created between the bandsaw blade and the peripheral surfaces of the bandsaw wheels. Slippage of the bandsaw blade on the bandsaw wheels will damage the bandsaw blade by slowing the blade down as it is forced into the workpiece. Although the slippage of the bandsaw blade can be overcome to some extent by increasing the tension of the bandsaw blade between the bandsaw wheels, too much tension will also cause premature blade wearing and breakage.
Thus, it will be seen that there exists a real need for an improved horizontal bandsaw machine incorporating means for both eliminating or at least substantially minimizing both blade vibration and slippage.